R2BayesX (version 0.3-1)

read.gra: Read Geographical Information in Graph Format

Description

Reads the geographical information provided in a file in graph format and stores it in a map object.

Usage

read.gra(file, sorted = FALSE, sep = " ")

Arguments

file

the file path of the graph file to be read.

sorted

logical. Should the regions be ordered by the numbers specifying the region names (sorted = TRUE)?

sep

the field separator character. Values on each line of the file are separated by this character.

Value

• Returns an adjacency matrix that represents the neighborhood structure defined in the graph file. The diagonal elements of this matrix are the number of neighbors of each region. The off-diagonal elements are either -1 if regions are neighbors else 0.

Details

A graph file stores the nodes and the edges of a graph and is a convenient way to represent the neighborhood structure of a geographical map. The structure of a graph file is given by:

• The first line of the graph file specifies the total number of nodes.
• The subsequent three lines correspond to the node with the name given in line 2, the number of neighbors in line 3 and the neighboring node identity numbers in line 4.

Note that the note identity numbering starts with 0. Example taken from the package example file Germany.gra: l{ 309 1001 1 1 1059 3 0 3 4 1002 2 5 4 1051 3 4 1 9 1058 7 2 6 3 5 1 10 9 ...} Hence, this graph file contains of 309 regions. The first region with name 1001 has 1 neighbor with neighboring node identity number 1. The last region in this example, region 1058, has 7 neighbors with neighboring node identity numbers 2 6 3 5 1 10 9. In addition, graph files using the following format may be imported:

• The first line of the graph file specifies the total number of nodes.
• The subsequent lines start with the node name followed by the number of neighbors and the neighboring node identity numbers.

Example: l{ 309 1001 1 2 1059 3 1 4 5 1002 2 6 5 1051 3 5 2 10 1058 7 3 7 4 6 2 11 10 ...}

References

BayesX Reference Manual, Chapter 5. Available at http://www.BayesX.org.

See Also

write.gra, read.bnd, write.bnd, get.neighbor, add.neighbor, delete.neighbor.

Examples

file <- file.path(find.package("R2BayesX"), "examples", "Germany.gra")
germany <- read.gra(file)